Homefix: Proper insulation

Saturday

Aug 20, 2011 at 12:01 AMAug 20, 2011 at 7:17 PM

Q: My home is 35 years old and I have a contract with Orkin for re-inspection for termites every year. The representative told me I needed to replace my insulation; he said part of it was hanging down and it was wet. He recommended their insulation, which is encased in plastic and stapled to the floor joist. I can't find any information on this method. Will this trap moisture on the sub floor and cause more problems? I have plastic ground cover, a sump pump and vents in the crawlspace.

Dwight Barnett

Q: My home is 35 years old and I have a contract with Orkin for re-inspection for termites every year. The representative told me I needed to replace my insulation; he said part of it was hanging down and it was wet. He recommended their insulation, which is encased in plastic and stapled to the floor joist. I can't find any information on this method. Will this trap moisture on the sub floor and cause more problems? I have plastic ground cover, a sump pump and vents in the crawlspace.

A: If you live in a very cold climate, insulating in between the floor joists can save some energy. However, in most climates, simply insulating the foundation walls and rim joists should be sufficient and will help to control humidity levels in the crawlspace. There are homes with radiant heat from ceiling panels while others are heated by hydronic hot-water heating systems with pipes integrated into the floor system.

In both cases, the floor joist cavities of these homes need to be insulated. Homes with forced-warm-air systems most likely use the crawlspace area for the ductwork that distributes conditioned air to each room, ductwork that returns the air from several rooms or both supply and return ducts that may be found side by side. By separating the ducts from the floor system with insulation, you are losing radiant energy produced by the supply-side ductwork.

Wet insulation or insulation installed upside down must be removed to prevent decay and mold formation. Ninety-nine percent of the homes I inspect that have fiberglass insulation in the floor system have the Kraft paper or foil-faced covering installed facing the unconditioned area of the crawl -- what I refer to as "upside down." This may be the easiest way to install the insulation, but it is the wrong way and the paper or foil barrier will hold moisture between the facings and the underside of the home's floors. Moisture accumulates in the cavity along with rodent droppings and nesting materials, and you have a very nasty and unhealthy situation.

My advice is to remove the floor joist insulation, insulate all the perimeter foundation walls including the walls next to an attached garage or porch, seal all crawlspace vents, insulate and weather-seal the crawl-access door and have an HVAC (heating-venting-air conditioning) technician introduce air supply from the warm-air furnace to the crawlspace.

Do not add a return air source because the idea is to pressurize the crawlspace to prevent air leaks from the outside. A warm and cozy crawlspace will reduce energy use, reduce humidity levels and the chances for mold growth; without moisture, a dry crawlspace will discourage unwanted pests. You still need to have the home inspected annually for termites because these wood-destroying insects bring their own water supply with them from the soils under the home.

I would also recommend a pump alarm for the sump pump to warn you of a pump failure and the possibility of a flooded crawl.

Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, IN 47702 or email him at d.Barnett@insightbb.com.

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